1. Field of the Invention
The present invention relates to a distance-measuring sensor. In more detail, the present invention relates to a distance-measuring sensor of a distance-measuring device which is used in a camera, etc. and utilizes a phase difference mode in the trigonometric survey. In addition, the present invention relates to the above distance-measuring device or camera using the above distance-measuring sensor.
2. Description of the Related Art
Recent sensors used in distance-measuring devices are benefited by the rapid progress of semiconductor manufacturing techniques and circuit design techniques. Microfining and area formation (a migration from a line sensor to an area sensor) are advancing, and the number of photoelectric conversion elements used in distance measurements tends to increase. Distance-measuring devices measure the distances of multiple places of an object (multipoint distance measurement). Therefore, it becomes possible to analyze a field all over to detect an object by increasing the number of distance measurement places. Accordingly, a camera user need not be concerned with focusing for a photograph and can devote their attention to composition. Of course, the probability of taking a fuzzy photograph also decreases.
Thus, an increase in the number of image elements of photoelectric conversion elements makes a contribution to the high performance of a distance-measuring device. On the other hand, output data for each image element (written as an object image signal hereafter) are memorized and stored into an external memory outside a sensor, and the distance to an object is commonly calculated by an arithmetic part outside the sensor using the data stored in this external memory. Therefore, the increase in the number of image elements of the photoelectric conversion elements causes such new requirements such as a large, memory capacity of external memory and an increase of transmission time for transmitting the object image signal to the external memory.
A technique in which all distance-measuring calculations made by a distance-measuring device are performed in a distance-measuring sensor, has been known to resolve these new requirements. In this distance-measuring device, only the final data are output and stored in an external memory, while the distance-measuring calculations are made inside the distance-measuring sensor. Therefore, it enables one to save the external memory capacity and shorten the transmission time of data output.
However, in the above distance-measuring device, such problems as the large memory capacity for storage and the increase of data transmission time, being the mentioned side effects of the high image element of the photoelectric conversion elements can be solved. A new problem of reducing the universality of the distance-measuring sensor arises, because all the processing has to be executed in the distance-measuring sensor.
In distance measurement, the universality is important for giving the processing the characteristics that correspond to an object to improve the distance measurement accuracy. For example, the distance measurement of a phase difference mode holds such a principled problem that the distance measurement accuracy of a low-contrast object is bad due to the properties of a phase difference calculation. Accordingly, when the distance measurement of a low-contrast object is made by the phase difference mode, a measure for giving a differential processing to an object image signal (e.g., obtaining a difference of an adjacent object image signal) and then performing a phase difference calculation has been conceived.
Namely, it is possible to improve the distance measurement accuracy by giving the processing in response to an object to an object image signal. However, in a distance-measuring sensor of such a simplified construction (a low universality) that only a phase difference calculation for a common object is performed, a differential processing for such a hard-to-handle object cannot be performed. Thus an improvement of the distance measurement accuracy cannot be achieved. Conversely, if all the processing including this processing is executed in a distance-measuring sensor, the circuits in the distance-measuring sensor are complicated and an increase in the cost of the distance-measuring sensor is induced.
The present invention was made in view of the above circumstances. The present invention is aimed at providing a distance-measuring sensor which does not impair the universality, suppresses the requirement of a large memory capacity for storage and an increase of data transmission time and is usable in the construction of a distance-measuring system.
To achieve the above purpose, the distance-measuring sensor based on the present invention has a light-receiving part with multiple photoelectric conversion elements for converting a light from a distant measured object to an electric signal corresponding to the intensity of the light, an arithmetic part for calculating the intermediate data of a distance calculation based on.the electric signal output by the above light-receiving part, and an output part for outputting the intermediate data calculated by the distance calculation. In this distance-measuring sensor, the arithmetic is performed in the above distance-measuring sensor until the intermediate data of the distance calculation, and the intermediate data are output. For example, the CPU receives the intermediate data and executes a residual distance calculation externally. Thus, the data quantity output is small as compared to a case where all of the data are output without applying an arithmetic calculation to the photoelectric conversion data, because the arithmetic is performed until the intermediate data of distance calculation in the distance-measuring sensor of the present invention. Moreover, the capacity of the external memory is also small. Furthermore, the universality is also impaired little because of the output at the intermediate data stage.
The above intermediate data calculated in the arithmetic part of this distance-measuring sensor are preferably values calculated one by one by repeated calculations. In such a way, the distance-measuring sensor may output only one intermediate data rather than a large quantity of data groups for arithmetic calculation. Therefore, the time for transmitting the output data is greatly reduced. Moreover, a function for changing the data and repeating the same arithmetic and a function for judging the conditions to get rid of the repetition are necessary, thus a complicated circuit construction is needed. Therefore, the complication of the distance-measuring sensor can be avoided by not performing all the repeated calculations with the distance-measuring sensor.
This distance-measuring sensor is preferably used in the distance measurement by the phase difference detection method. This distance-measuring sensor is located such that a divided light beam from an object irradiates different portions of the light-receiving part (the portions do not overlap). This distance-measuring sensor also has a region-assigning part for assigning regions in respective portions irradiated by the divided light beam on the light-receiving part. The arithmetic part performs the arithmetic for comparing photoelectric signals generated in the regions.designated by this region-assigning part (more specifically, data based on generated photoelectric signals) with each other, and the results (correlated values) are obtained as intermediate data of distance measurement. The region assignment given by the region-assigning part are repeatedly performed by changing positions one by one, the arithmetic part calculates the intermediate data for every region assignment and outputs the intermediate data from the output part externally (e.g., CPU). Thus, repeated calculations for obtaining the correlated values between the regions are performed by a phase difference detection method, but this distance-measuring sensor obtains the correlated values calculated one by one by the repeated calculations as the intermediate data and outputs the data externally. Therefore, this distance-measuring sensor does not need a complicated circuit construction and restrains the transmission time of the output data.
The region-assigning part of this distance-measuring sensor preferably assigns the regions by external assignment. It enables one to flexibly change the selection methods of the regions according to an object. For example, a selection of arithmetic processing corresponding to the contrast of a distance measured object is enabled in a distance calculation by the phase difference detection method. More specifically, an effective region (non-shielded region) and a light shielded region (a region shielded so that a light does not irradiate) are provided in the light-receiving part. If a distance measured object has a common contrast, the regions are selected from the effective region and the light shielded region and a difference between the output of effective region and the output of light shielded region is obtained to cancel noises due to a dark current. On the other hand, if the contrast of a distance measured object is low, two adjacent or partly overlapped regions are selected in the effective region, and a difference of the outputs of adjacent photoelectric conversion elements is calculated to differentiate (difference) the outputs.